Many devices that produce artificial light do so on a discontinuous basis. For example, incandescent or fluorescent lights produce light from an alternating current power source that operates at 50-60 cycles per second (Hz). In most cases, the artificial light produced by such devices appears to most people to be uninterrupted, continuous light.
In some cases, the devices that produce such light may begin to malfunction and produce a noticeable flicker, such as for example, a fluorescent light. A malfunctioning fluorescent light that flickers, however, is only a minor irritation to most people.
Similarly, television sets, video games and movies operate by dividing images into a series of image frames that are presented to a viewer at a predetermined frame rate. In the case of television, the frame rate is 30 frames per second.
In order to reduce any flicker and to produce the effect of a more continuous image, television sets use a concept called interleave scanning. Under interleave scanning, a television set divides the screen into odd and even horizontal lines. To present an image, a controller of the television presents a first image on the odd lines followed by a second image on the even lines followed by a third image again on the odd lines and so on.
In general, most people are not able to process information fast enough to perceive the changing images. In most cases, the inability of the human visual system to process high speed optical signals operates effectively, to make such changing optical signals appear to be a continuous image.
However, some visual images are not always perceived as continuous. For example, equipment malfunction, laser battles between players in video games or even explosions in movies can cause severe neural disruptions in some people, leading to headaches and, in some cases, epileptic seizures. Because of the dangerous health effects, a need exists for a method of avoiding the effects produced by such images or series of images.